This study investigated a long-term climatology of nocturnal equatorial F-region irregularities by using phase fluctuations of the global positioning system during the solar cycle of 1996-2006 at the west Pacific longitudes. The results showed that the distribution of the occurrence of irregularities is a two-peak pattern, which peaks in equinoxes with a shallow/deep dip in June/December solstice during high solar activity but with two about the same dips in magnitude in both June and December solstices during low solar activity. Moreover, the most interesting longitudinal effect in the area is in solstice occurrences of irregularities during high solar activity that the irregularities in December solstice months develop easier in the west area but those in June solstice months develop easier in the east area. (C) 2008 Elsevier Ltd. All rights reserved.
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS